Method for transferring a toner image

ABSTRACT

A toner image is transferred from a toner substrate to a transfer sheet by bringing the toner substrate and the transfer sheet into face to face contact and applying a vibration thereto, while simultaneously applying pressure and/or an electrical field across the substrate and transfer sheet.

United States Patent 1 91 S Sato et al.

[ METHOD FOR TRANSFERRING A TONER IMAGE [75] Inventors: Masamichi Sato,Tucson, Ariz.;

Osamu Fukushima, Tokyo, Japan [73] Assignee: Xerox Corporation,Stamford,

Conn.

[22] Filed: Feb. 20, 1973 I [21] Appl. No.: 333,825

301 Foreign Application Priority Data Aug.28, 1970 Japan "45-75321 [52]US. Cl....;....., 117/17, 9 6/l.4, 117/17.5, 117/37 LE, 117/DIG. '8,118/57, 118/637 {51] Int. Cl. G03g 13/16, G03g 15/16 [58] Field ofSearch l17/3.1, 16, 17, 17.5, 117/37 LE, DIG. 8; 96/1 R, 1.4; 118/637,57;

[ Dec. 17, 1974 [56] References Cited UNITED STATES PATENTS 2,843,4997/1958 Andrus 1l7/17.5 3,328,193 6/1967 Oliphant et al.... 118/6373,399,111 '8/1968 Beaumont eta1.. 156/73 3,541,671 ll/l970 Frachot156/73 3,653,948 4/1972 Kaernpgen et al. 118/57 3,658,519 4/1972 Men;96/1.4 3,691,993 9/1972 Krause et al ll7/l7.5 3,698,314 10/1972Grier...) 117/21 Primary E.raminer -Michael Sofocleous [57] ABSTRACT Atoner image is transferred from a toner substrate to a transfer sheet bybringing the toner substrate and the transfer sheet into face to facecontact and applying a vibration thereto, while simultaneously applyingpressure and/or an electrical field across the substrate and transfersheet.

9 Claims, 1 Drawing Figure METHOD FOR'TRANSFERRING A TONER IMAGEBACKGROUND AND SUMMARY OF Tl-IE INVENTION,

The present invention relates to a method and apparatus for transferringa toner image from a substrate to a receiving element such as a transfersheet, and is particularly applicable to the transfer of atoner imageobquency vibration thereto, while applying an electric field and/orpressure across the interface.

In the field of electric photography it is often necessary to transfer atoner image developed on one substrate to a transfer sheet. It is wellknown in the prior art to effect such transfer by employing such methodsas electrostatic attraction, mechanical pressing and tacky adhesion. Inthe electrostatic method, a transfer sheet is brought into contact withatoner substrate and a corona discharge is applied to the rear surfaceof the transfer sheet to attract the toner thereto. In the mechanical-pressing method, a toner substrate is disposed on a transfersheet and the "composite is conveyed through a pair of opposing pressurerollers, whereby the toner particles are caused to adhere to thetransfer sheet. The tacky adhesion method is one in which a transfersheet containing a tacky layer is pressed against the surface of thetoner substrate, to transfer the 'toner image from'said substrate tothetransfer sheet adhesively.

According to the present invention, an effective I methodand apparatushas been developed for transferring a toner image from a toner substrateto atransfer sheet, wherein the toner substrate and transfersheet arebrought together, in face to face contact, and a high frequency lowamplitude vibration is applied to said substrate and sheet while theyarein contact with each other. -Any suitable means can be used to bringthe toner substrate and transfer she'etinto mutual contact, such as forexample, a pair of rollers, and thevibration can-be ofmechanic'al orelectrical origin. In the case where a pair of opposed rollers are used,the vibration can be applied to the rollers at the point where the tonersubstrate and the transfer sheet are brought into contact with eachother, that is, where they pass through the nip of the rollers. Thevibration of the rollers is transferred to said substrate and transfersheet while they are in contact with each other. Simultaent to thoseskilled in the artfrom this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will-become morefully understood from the detailed description given hereinbelow inconjunction with the accompanying drawings, which are given by way ofillustration only and thus are not limitative of the present invention,and wherein the single FIGURE of thef'present invention shows aschematic illustration of a side view of an apparatusfor transferring atoner image from a toner substrate to a transfer sheet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of thepresent invention shown in the drawing, a toner substrate 3 containingtoner image 4 formed thereon is conveyedtogether with a transfer sheet 5through the nip of a pair of opposed pinch rollers 1 and 2. A vibrator 7bears against the axle of roll 2 to produce a vibration which, in theembodiment shown, is substantially perpendicular to the direction oftravel of the-toner substrate and transfer sheet and is I applied to thesubstrate 3 and sheet 5 at the nip of the rollers. Alternatively, thevibrator may be positioned to contact any part of roller 2, or any partof roller I if desired. The amplitude of vibration of the roller can bement, wherein a vibration is applied .to said substrate andelement whilethey are in contact with each other.-

Another object of the present invention is toprovid e a method andapparatus for transferring a toner image from a toner substrate to atransfer sheet wherein, in addition to said vibration. the tonersubstrate and the varied widely, though it is preferred to be in therange of about several microns to several hundred microns. The.frequency of vibration. is somewhat dependent upon the running speed ofthe rollers. For example, where the running speed of the rollers isslow, the frequency of vibration may also be relatively small, whereaswhen the rollers are running at a fast speed, the frequency would haveto be proportionately greater. When the rollers are running at a speedof about 5 cm/sec., the frequency of vibration is preferred to be about1,000 H, or more. When the rollers are running at a speed of about 5cm/sec., but the frequency is only about 100 H,, the length of eachcycle as projected on the transfer sheet would be about 0.5 mm, whichwould cause toner transfer in streaks of 0.5mm intervals, giving anunacceptable print. If, however, the frequency is increased to about1,000 Hz. it is difficult to see any streaks because the lengthof eachcycle is reduced to about 0.05 mm.

The vibrator may be driven by a piezoelectric element or amagnetostrictive element to which an alternating current is applied inorder to obtain the desired vibration. Alternatively, the vibrator mayutilize a me-.

' chanical drive.

I Toner transfer'from the substrate 3 to the transfer sheet 5 iseffected by a combination of the vibratory action above-described withthe simultaneous application of mechanical pressure and/or an electricalvoltage across the toner substrate and transfer sheet at the '3 point oftoner transfer. For example, in the case where superimposed rollers areused, thepressure is applied between the rollers at the point ofcontact, and can be the result simply of the weight of the upperr'ollerdisposed upon the lower roller, of if an additional force isdesired,theupper roller can be weighted. An electrical field across thenip of rollers. l and 2 can be provided by dc power source 6. Thepolarity of the power source is selected to provide an opposite polarityon roll 1 backing the transfer sheet 5, from the residual electrostaticcharge on the toner particles 4. A protective resistance R is preferablyinserted in the electrical circuit which may have a value of between 20and 1,000 kiloohms.

The pinch rollers l and 2 may, for example, be made of steel, oralternatively, one of the rollers can be a metal roller whereas theother can comprise a metal core covered with an electroconductivematerial, a semi-conductive material or an insulating rubber. The

toner substrate 3 may comprise, for example, a sheet of EXAMPLE 1 Thetoner image transfer apparatus comprises two superimposed stainlesssteel rollers, each having a smooth surface and a diameter of 20 mm. Thebearing of the lower roller is fixed and is driven at a speed of 2cm/sec. by'means of a motor and through the use of a gear reductionsystem. The'upper roller is supported by a bearing-which is freely selfadjusting vertically. The upper roller is superimposed on the lowerroller andis driven by the friction created by its weight on the lowerroller as the latter rotates. When a toner substrate together with atransfer sheet are feed in face to face contact between the two rollers,the upper roller rises from the lower roller a distance equivalent tothe thickness of both materials, and a pressure equivalent to the weightof the upper roller is applied between the rollers. The upper roller isnegatively charged from a direct current supply of 1,500 volts, and forsafety purposes a resistance of l00,000 ohms is provided in theelectrical circuit. A vibrator is in contact with the shaft of the lowerroller for vibrating the same at L000 H,.

An electrophotographic substrate comprising electrophotoconductive zincoxide and an insulating resin coated on a sheet of paper is exposed, anddeveloped with a toner of carbon black coated with a resin and suspendedin kerosene. thereby producing a toner image onthe substrate. The tonerhas a positive charge. After the toner image is formed, the tonersubstrate is brought into contact with a transfer sheet while in a wetstate and passed through the above-described transfer apparatus.Ordinary paper is employedas the transfer sheet. Transfer is carried outuniformly and a high quality'transferredimage is obtained. Good resultswere also obtained using a vibration frequency of 10 K Hg.

EXAMPLE ll EXAMPLE "I 7 Uniform transfer of the toner image from thetoner substrate to the transfer sheet is obtained. using the ap paratus,method andmaterials of Example 1, except no voltage is applied acrossthe rollers, and instead, the roller pressure is increased by theapplication of a force of 4 Kg between the rollers. Good results arealso obtainedwith a vibration frequency of 29 K H,.

EXAMPLE [V In this Example uniform transfer of the tonerimage from thetoner substrate to the transfer sheet i's obtained as in Examplell,except no voltage is applied across-the rollers, and instead,therolle'rpressure is increased by the applicationof a force of 6 Kg between therollers. Also, the upper stainless steel roller in Example II isreplaced by a roller having a 10 mm diameter metal core and a 5 mm thickrubber coating. Using a vibration frequency of 1,000 H good transferresults were achieved.

Although, in the above Examples, only one pair of rollers is used, aplurality of pairs of rollers may be employed if it is desired tooperate at high speeds.

The invention being thus described, it will be obvious to one skilled inthe art that the same may be varied in many ways. Such variations arenot to be regarded as departures from the spirit and scope of theinvention, and all modifications as are embraced by the appended claimsare intended to be included within the purview of the present invention.

What is claimed is:

l. A method of transferring a toner image from a toner substrate to atransfer sheet which comprises bringing the toner substrate bearing thetoner image and the transfer sheet together into face to face contact,vibrating said substrate and said sheet while they are in contact witheach other and simultaneously applying a transfer means to effect thetransfer of said toner image to said transfer sheet.

2. The method as defined in claim 1, wherein said transfer meanscomprises applying an electric field across the substrate and the sheet.

3. The method as defined in claim 1 wherein said transfer meanscomprises applying pressure across the substrate and the sheet. a

4. The method as defined in claim 1, wherein the vi bration issubstantially perpendicular to the direction of travel of the tonersubstrate and the transfer sheet.

said rollers is at least about 200 H per cm/sec.

8. The method as defined in claim 1, wherein the toner substratecomprises a sheet of paper coated with a mixture including aphotoconductive zinc oxide powder andan insulating resin.

9. The method as defined in claim 1 wherein the transfer sheet isselected from the group consisting of a paper material, a plastic filmand a paper material coated with a plastic film.

1. A METHOD OF TRANSFERRING A TONER IMAGE FROM A TONER SUBSTRATE TO ATRANSFER SHEET WHICH COMPRISES BRINGING THE TONER SUBSTRATE BEARING THETONER IMAGE AND THE TRANSFER SHEET TOGETHER INTO FACE TO FACE CONTACT,VIBRATING SAID SUBSTRATE AND SAID SHEET WHILE THEY ARE IN CONTACT WITHEACH OTHER AND SIMULTANEOUSLY APPLYING A TRASNFER MEANS TO EFFECT THETRASNFER OF SAID TONER IMAGE TO SAID TRANSFER SHEET.
 2. The method asdefined in claim 1, wherein said transfer means comprises applying anelectric field across the substrate and the sheet.
 3. The method asdefined in claim 1 wherein said transfer means comprises applyingpressure across the substrate and the sheet.
 4. The method as defined inclaim 1, wherein the vibration is substantially perpendicular to thedirection of travel of the toner substrate and the transfer sheet. 5.The method as defined in claim 1, wherein the vibration has an amplitudeof about several microns to several hundred microns.
 6. The method asdefined in claim 1, wherein the toner substrate and transfer sheet arebrought together between the nip of at least a pair of rotating rollerswith the vibration being applied to at least one of said rollers.
 7. Themethod as defined in claim 1, wherein the ratio of frequency ofvibration to peripheral velocity of said rollers is at least about 200Hz per cm/sec.
 8. The method as defined in claim 1, wherein the tonersubstrate comprises a sheet of paper coated with a mixture including aphotoconductive zinc oxide powder and an insulating resin.
 9. The methodas defined in claim 1 wherein the transfer sheet is selected from thegroup consisting of a paper material, a plastic film and a papermaterial coated with a plastic film.